Mechanically nutating drill driven by orbiting mass oscillator

Abstract

A drill bit is coupled at its upper end to an orbiting mass oscillator. The oscillator is mounted and connected to the bit such that the oscillator describes a conical orbiting path. The drill bit follows this conical orbiting path of the oscillator which results in a rolling nutating action of the bit cutters on the work material.

I claim: 
     
       1. A drilling system for drilling through hard material, such system including a drilling bit, the improvement comprising means for cyclically nutating said bit at a sonic frequency comprising: an orbiting mass oscillator having a rotor,   means for connecting said oscillator to said bit for freedom of rotation in a conical orbiting path,   means for biasing said bit against the material being drilled, and   means for rotatably driving said oscillator rotor in an orbiting path,   said oscillator being caused to vibrate in a conical path so as to generate conical vibratory energy, said conical vibratory energy being transferred to said bit, with the top of said oscillator forming the base of the cone and said drill bit nutating at the oscillator frequency around said work material.   
     
     
       2. The device of claim 1 wherein said oscillator has a screw-type rotor and said means for rotatably driving said rotor comprises means for feeding a mud stream to said oscillator. 
     
     
       3. The device of claim 1 or 2 wherein said bit is a roller cone bit. 
     
     
       4. The device of claim 1 wherein said means for connecting said oscillator and said bit for freedom of rotation in a conical orbiting path comprises universal joint means. 
     
     
       5. The device of claim 1 wherein the oscillator rotor is a screw member, said oscillator having a housing with a screw-shaped internal wall portion which mates with the rotor screw member. 
     
     
       6. The device of claim 1 or 2 and further including means for rotating said bit about the longitudinal axis thereof at a frequency susbstantially lower than said sonic frequency. 
     
     
       7. The device of claim 1 or 2 and further including a jacket member and means for mounting said oscillator in said jacket member whereby said jacket member limits the excursion of the oscillator orbit. 
     
     
       8. The device of claim 1 wherein said means for interconnecting the oscillator and the bit for freedom of rotation in an orbital path comprises a resilient bushing.